The invention relates, generally, to abrasive blast machines and, more particularly, to an improved bolt-together blast wheel for such machines.
Abrasive blast machines typically consist of a housing rotatably supporting a blast wheel. The blast wheel typically consists of a pair of side plates secured together so as to support a plurality of radially extending blades therebetween as shown in Freeman, U.S. Pat. No. 3,785,105. A drive motor rotates the blast wheel at high speeds and abrasive particles are fed onto the blades as the wheel rotates. The centrifugal force of the rotating wheel propels the abrasive particles from the blades onto a surface being cleaned or otherwise treated.
Because the abrasive particles are relatively small, the blast wheel rotates at high speed and the shot is rebounding from the blades, the surface being cleaned and other components of the blast machine, the abrasive shot undergoes frenetic and uncontrolled movement. As a result, the shot contacts virtually all the interior surfaces of the blast machine. Because abrasive particles consist of small pellets or metal shot or other material they are highly abrasive and cause wear on the components of the blast machine which they contact. The wear is significantly increased in areas where there are projections, depressions, cavities or other non-uniform surfaces because of the abrasive's repeated impact in these areas. Thus, it is desirable to make the surfaces of blast machine components, such as blast wheels, as smooth and uniform as possible.
Because the components of the blast wheel are subject to wear, they must be replaced regularly. It is also desirable, therefore, to make the blast wheel as simply and inexpensively as possible.
Blast wheels such as those illustrated in Freeman, although providing relatively uniform surfaces, are difficult to manufacture because the spacers 16 must be swagged or riveted in place. These manufacturing processes are relatively time consuming and require expensive machinery such as presses. Moreover, swagging requires relatively soft metal because the metal must be deformed during the manufacturing process and, as will be apparent, the use of soft metals results in increased wear. Blast wheels that use bolts, such as Minich, U.S. Pat. No. 2,049,466, are relatively simpler to manufacture. However, the protruding nut and bolt arrangement will increase wear as the abrasive material impacts the exposed surfaces.
Thus, an inexpensive, simple to manufacture, low wear bolt-together blast wheel is desired.